Sewage sludge as a sustainable fertilizer: Promise, pitfalls, and future directions

Sewage sludge (SS) management and its application as a low-cost fertilizer remain a topic of debate among researchers due to its potential to contain microbial pathogens and pollutants. In this context, the composition of SS and its contemporary management practices are reviewed. Furthermore, the sustainable application of SS in agriculture and the effects of its components on human health are outlined. Several studies have found that using SS as a fertilizer reduces farmers’ agrochemical expenses. Despite its rich source of nutrients for crops and its practical agricultural applications in the United States, India, Europe, Australia, and various regions of the world, pathogens and pollutants limit its sustainable use. A wide diversity of pathogens, including bacterial strains ( Salmonella Typhi, Escherichia coli , Helicobacter pylori ), protozoan parasites ( Entamoeba histolytica , Toxoplasma gondii ), and viruses (rotavirus, norovirus, hepatitis A and E) exist in SS. On the other hand, antibiotic-resistant genes pose a significant threat and can increase the global burden of disease if they are introduced into soil. Additionally, microplastics (MPs), nanoplastics, and heavy metals (such as cadmium, arsenic, chromium, mercury, and lead) can be detrimental to human health, affecting the gastrointestinal, respiratory, and other systems. Concerns about the toxicity of MPs and nano-plastics have been increasing; however, the investigations are limited. It is crucial to emphasize the need for innovative techniques for pathogen removal and pollutant remediation, as this serves as a call to action for the scientific community to transform SS from waste into a valuable resource. • Global strategies for sewage sludge (SS) management are summarized. • Micro/Nano plastics, heavy metals, and microbial pathogens exist in SS. • SS and SS-based fertilizers have the potential to support sustainable agriculture. • Environmental considerations related to heavy metals should be taken into account. • Scientific views on the fertilizer potential of SS often differ and require evidence.